Establishment and digital simulation of upper airway in patients with adenoid hypertrophy / 中华口腔医学杂志

ABSTRACT

Objective: To analyze the flow field characteristics of the upper airway in patients with different adenoid hypertrophy using computational fluid dynamics (CFD). Methods: From November 2020 to November 2021, the cone-beam CT (CBCT) data of 4 patients [2 males and 2 females,age range 5-7 years, mean (6.0±1.2) years] with adenoid hypertrophy who were hospitalized in the Department of Orthodontics and the Department of Otolaryngology at Hebei Eye Hospital were selected. The degree of adenoid hypertrophy in the 4 patients was divided into normal S1 (A/N<0.6), mild hypertrophy S2 (0.6≤A/N<0.7), moderate hypertrophy S3 (0.7≤A/N<0.9) and severe hypertrophy S4 (A/N≥0.9) according to the ratio of adenoid thickness to the width of nasopharyngeal cavity (A/N). The CFD model of the upper airway was established using ANSYS 2019 R1 software, and the internal flow field of the CFD model was numerically simulated. Eight sections were selected as observation and measurement planes for flow field information. Relevant flow field information includes airflow distribution, velocity variation, and pressure variation. Results: In the S1 model, the maximum pressure difference occurred in the 4th and 5th observation planes (ΔP=27.98). The lowest pressures and the maximum flow rates of S2 and S3 were located in the 6th observation plane. The airflow in S1 and S2 models completely passed through the nasal cavity. In the S3 model, the mouth-to-nasal airflow ratio was close to 2∶1. In S4 model, the airflow completely passed through the mouth; in the S1 and S2 models, hard palates were subjected to a downward positive pressure with a pressure difference of 38.34 and 23.31 Pa, respectively. The hard palates in S3 and S4 models were subjected to a downward negative pressure with a pressure difference of -2.95 and -21.81 Pa, respectively. Conclusions: The CFD model can objectively and quantitatively describe the upper airway airflow field information in patients with adenoid hypertrophy. With the increasing degree of adenoid hypertrophy, the nasal ventilation volume gradually decreased, whereas the oral space ventilation volume gradually increased, and the pressure difference between the upper and lower surfaces of the palate gradually decreased until the pressure became negative.